This invention relates to hand tools, and in particular the invention is concerned with a compact hand tool, generally in the size and shape of a tape measure, for projecting a laser beam for use in relatively precise plumbing and leveling operations. The device has a further use of projecting a pointing beam for use in alignment or layout.
A variety of survey and carpentry tools have previously employed lasers. For example, see U.S. Pat. Nos. 3,897,637, 3,771,876, 4,221,483, 4,679,937, 4,781,457, 4,852,265 and 4,912,851.
In U.S. Pat. No. 3,897,637, there is disclosed a level and squaring tool utilizing a helium-neon laser for projecting a beam both vertically and horizontally. The device was not self-leveling and required manual leveling. It was rather large and required connection to an external source of power.
U.S. Pat. No. 3,771,876 was directed to a laser apparatus for producing a plane or conical optical reference surface. The device used a pendulum hanging from a flexible suspending member, with the pendulum containing the light source so as to be self-leveling. A double mirror or prism device was used for reflecting the beam out of the device 90 degrees from the entry angle of the beam from the pendulum. The double mirror (sometimes called a pentaprism) device was fixed in the unit and allowed for changes in the angle of the approach of the light beam from the pendulum.
Rando U.S. Patent No. 4,221,483, assigned to the assignee of the present invention, discloses a laser beam level instrument using the principle of translation of a lens which collimates a laser diode beam in order to compensate for small degrees of tilt in the instrument. The collimating lens is suspended as a pendulum and has the effect of maintaining the collimated beam in a truly vertical position providing self-leveling in a limited range of movement of the instrument.
U.S. Pat. No. 4,679,937, also assigned to the same assignee as the present invention, discloses a self-leveling battery-powered surveying tool. The tool, which is designed to be set up on a tripod, provides a reference for leveling and alignment. The apparatus, which includes a laser diode as a light source for projecting a generally horizontal but non-planar cone of light from a reflecting cone, includes a tilt compensation arrangement relevant to the present invention. The reflecting cone is suspended by a wire having a controlled stiffness which allows the mirror cone to tip at an angle which is one-half the angle of tilt error of the instrument from true plumb.
A contractor's tool for referencing a chosen elevation at a building site was marketed in the 1970s as Model 840 Building Laser, by the assignee of the present invention. The product also was capable of emitting a vertical beam. It had a helium-neon laser and was powered by an internal battery. The device was not self-leveling.
U.S. Pat. Nos. 4,852,265 and 4,912,851, also commonly owned with the present invention, disclosed level, plumb and alignment tools utilizing a laser diode and having tilt compensation means for small tilt variations from levelness of the housing. The device compensated for tilt in either of two directions of variation from true horizontal of the housing, such as when the tool was placed on a non-level section of floor. It was stated that the device compensated for tilt errors of up to about five degrees, while still projecting a beam from the tool in substantially true vertical or substantially true horizontal orientation.
In order to achieve the ability to project either a truly vertical or horizontal beam, the level/plumb tool of the latter two patents utilized a single pendulum-type tilt compensator in a preferred embodiment, with switching of the output beam's orientation achieved by rotating a dial wheel through 90.degree.. The rotation of the dial wheel moved a two-mirror right angle deflector onto the path of a tilt-compensated vertical beam, deflecting it to horizontal. The housing itself, which in a preferred embodiment was somewhat like a level in shape, remained in the same orientation for both horizontal projection and vertical projection.
While the latter two patents referenced above disclosed an effective level, plumb and alignment tool, none of the previous devices was as compact, as versatile in operation, as easily transported and as rugged as the plumb, level and pointing beam device of the present invention as described below.